Elastic mounts have been used as devices to support an operator compartment or cabin (hereinafter referred to as a cabin) on a body of mobile construction equipment, such as a bulldozer, in order to improve the riding quality for the operator. As shown in FIGS. 9A and 9B, a floor 2 of a cabin 1 is secured to a frame 3 of the body of the mobile construction equipment through four elastic mounts 50La, 50Lb, 50Ra and 50Rb.
A cross-section of the elastic mount 50La is shown in FIG. 9C as an example of the construction of the four elastic mounts 50La, 50Lb, 50Ra and 50Rb. Annular rubber members 51a and 51b are disposed about a tubular spacer 52 with rubber members 51a and 51b being located on the top and bottom sides, respectively, of the floor 2 with the outer diameter of the spacer 52 being less than the diameter of the opening in floor 2 through which the spacer 52 extends, so that the spacer 52 does not directly contact the floor 2. The rubber members 51a and 51b are tightly attached to the frame 3 by a bolt 54 extending through a holding plate 53 and the spacer 52 into the frame 3. Vibrations generated on the body frame 3 are at least partially absorbed by the rubber members 51a and 51b so as to substantially dampen the vibrations traveling to the cabin 1, thereby improving the riding quality.
However, the rubber utilized for the elastic mounts 50La, 50Lb, 50Ra, and 50Rb is generally a hard rubber having a large spring constant in order to improve the durability of the rubber members 51a and 51b. Accordingly, such elastic mounts are insufficient for absorbing large amplitude vibrations and shock. This makes the construction equipment uncomfortable to ride and causes early fatigue of an operator, which degrades working efficiency. At the same time, the use of hard rubber elastic mounts permits the formation of cracks and failures in the structure of cabin 1. In order to counter these problems, damper plate shock absorbers (viscous mount) having a smaller spring constant may be used in place of the elastic mounts 50La, 50Lb, 50Ra, and 50Rb. However, such viscous mounts are still insufficient for absorbing the shock caused to a bulldozer upon passing over a large rock or the like.
On the other hand, a flexible supporting structure having a small spring constant can be used effectively for absorbing the vibration and the shock. However, the cabin 1 may experience excessive oscillation upon the equipment passing over a large rock. A resulting lateral oscillation can result in interference between the cabin peripheral members and the frame 3, as well as in erroneous or incorrect operation of control levers located in the cabin 1.